“Planet Earth”?is known for its spectacular cinematography capturing nature in all its high-definition glory, and “Extreme Survival” continues that trend as it follows our planet’s heartiest animal inhabitants toughing it out in some of the harshest environments imaginable. Some of these locations are beyond belief — or at least it seems that way from our couch.

Can you imagine the inhospitable environs that polar bears must endure when the worst winter weather hits? How do they take a swim when the ocean is covered in ice? We’ll find out. And as usual, be amazed by the visual documentation “Planet Earth” delivers. Seriously, it’s as though we can see each individual strand of fur on those polar bears.

Narrated, as always, by world-renowned naturalist Sir David Attenborough, the hour documents examples of extraordinary survival by animals across an incredible range of landscapes and weather conditions — each a life-threatening challenge.

We think our world is coming to an end when we get spotty cell service in the mall food court. Can you imagine how elephants eat and drink enough to survive in the middle of the Namibian desert’s dry season? The riverbeds are bone-dry, and the only water flows underground. The desert elephants know the tricks of the trade.

Other stories of survival include gelada baboons in the highlands of Ethiopia, massive emperor penguins — they stand 4 feet tall and weigh up to 99 pounds — that can dive to depths of 1,755 feet, the bat-eating snakes that stalk the caves of New Zealand, the fascinating social behavior of bottle-nosed dolphins, and the peculiar story of the camels that eat snow in the extreme deserts of Mongolia.